"While diplomats argued over details of Annan's peace plan, Syrian tanks and helicopters attacked one town in Idlib after another," said Anna Neistat, associate director for programs and emergencies at Human Rights Watch.
"Everywhere we went, we saw burned and destroyed houses, shops and cars, and heard from people whose relatives were killed. It was as if the Syrian government forces used every minute before the cease-fire to cause harm," she said.
The report was based on a field investigation conducted in Idlib province. Some of the incidents cited appear to confirm widespread reports at the time of an offensive in Idlib in early April that triggered a wave of refugees who crossed the border to Turkey with horrific accounts of mass graves, massacres and burned out homes. Activists at one point reported about 100 dead in the villages of Taftanaz and Killi.
HRW said the majority of execution-style killings took place during the attack on Taftanaz. It cited nine separate incidents in which government forces executed 35 civilians in their custody. In other cases, government forces opened fire and killed or wounded civilians trying to flee the attacks.
Other groups, including the U.N.'s top human rights body, have condemned Syria for widespread and systematic rights violations against civilians.
The U.N.-appointed Independent International Commission of Inquiry on Syria has published two reports during the conflict. Last month, it handed U.N. human rights chief Navi Pillay a secret, sealed list of top Syrian officials who could face investigation for crimes against humanity.
Associated Press writer Albert Aji contributed reporting from Damascus, Syria.